Added the Ash.Tab.TimeBetweenSwitchToExistingTabUserActions histogram to track time between tab swit

ash/metrics/task_switch_metrics_recorder_unittest.cc

Index: ash/metrics/task_switch_metrics_recorder_unittest.cc
diff --git a/ash/metrics/task_switch_metrics_recorder_unittest.cc b/ash/metrics/task_switch_metrics_recorder_unittest.cc
index ca3078e3394086e02d4b464fd936265ca1f8802e..4851482bca4a20f2bad0bab44bf3e67ed5b2646b 100644
--- a/ash/metrics/task_switch_metrics_recorder_unittest.cc
+++ b/ash/metrics/task_switch_metrics_recorder_unittest.cc
@@ -92,4 +92,19 @@ TEST_F(TaskSwitchMetricsRecorderTest,
   histogram_tester_->ExpectTotalCount(kHistogramName, 2);
 }
 
+// Verifies that the TaskSwitchMetricsRecorder::kTabStrip source adds data to
+// the Ash.Tab.TimeBetweenSwitchToExistingTabUserActions histogram.
+TEST_F(TaskSwitchMetricsRecorderTest,
+       VerifyTaskSwitchesFromTheTabStripAreRecorded) {
+  const std::string kHistogramName =
+      "Ash.Tab.TimeBetweenSwitchToExistingTabUserActions";
+
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kTabStrip);
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kTabStrip);
+  histogram_tester_->ExpectTotalCount(kHistogramName, 1);
+
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kTabStrip);
+  histogram_tester_->ExpectTotalCount(kHistogramName, 2);
+}
+
 }  // namespace ash